Precision BEOL resistors

ABSTRACT

A semiconductor structure that includes a resistor that is located within an interconnect dielectric material layer of an interconnect level is provided. The resistor includes a diffusion barrier material that is present at a bottom of a feature that is located in the interconnect dielectric material layer. In some embodiments, the resistor has a topmost surface that is located entirely beneath a topmost surface of the interconnect dielectric material layer. In such an embodiment, the resistor is provided by removing sidewall portions of a diffusion barrier liner that surrounds a metal-containing structure. The removal of the sidewall portions of the diffusion barrier liner reduces the parasitic noise that is contributed to the sidewall portions of a resistor that includes such a diffusion barrier liner. Improved precision can also be obtained since sidewall portions may have a high thickness variation which may adversely affect the resistor&#39;s precision.

BACKGROUND

The present application relates to a semiconductor structure and amethod of forming the same. More particularly, the present applicationrelates to back-end-of-the-line (BEOL) resistors that have highprecision as well as methods of forming such BEOL resistors.

A resistor, which is a passive two-terminal electrical component thatimplements electrical resistance as a circuit element, is one of themost common electrical components present in almost every electricaldevice. In electronic circuits, resistors can be used to limit currentflow, to adjust signal levels, bias active elements, and terminatetransition lines.

In semiconductor devices, it is well known to have a thin film resistorsuch as, for example, a resistor composed of TaN, embedded in the chipthrough either a damascene approach or a subtractive etch method. Forexample, and during back-end-of-the-line (BEOL) processing, a thin filmresistor may be embedded in an interconnect dielectric material; suchstructures may be referred to as BEOL resistors. Prior art methods offorming thin film resistors embedded in an interconnect dielectricmaterial are complicated and expensive. Moreover, topography issuesarise when embedding a thin film resistor in an interconnect dielectricmaterial which may degrade the final chip yield. Other issues with priorart methods of embedding a thin film resistor in an interconnectdielectric material include, but are not limited to, Joule heating andpoor scaling capabilities.

Moreover, precision BEOL resistors used in analog circuits need to havesmall tolerances of variation and need to integrate in with the overallBEOL process flow in a way that minimizes cost, space and/or wiringcongestion.

SUMMARY

A semiconductor structure that includes a resistor that is locatedwithin an interconnect dielectric material layer of an interconnectlevel is provided. In accordance with the present application, theresistor comprises a diffusion barrier material that is present at abottom of a feature that is located in the interconnect dielectricmaterial layer. In some embodiments, the resistor has a topmost surfacethat is located entirely beneath a topmost surface of the interconnectdielectric material layer. In such an embodiment, the resistor isprovided by removing sidewall portions of a diffusion barrier liner thatsurrounds a metal-containing structure. The removal of the sidewallportions of the diffusion barrier liner reduces the parasitic noise thatis contributed to the sidewall portions of a resistor that includes sucha diffusion barrier liner. Improved precision can also be obtained sincesidewall portions may have a high thickness variation which mayadversely affect the resistor's precision. The semiconductor structureof the present application is devoid of any metallic structure thatcontacts a topmost surface of the resistor.

In one embodiment, the semiconductor structure includes a lowerinterconnect level including first metal-containing structures embeddedwithin a first interconnect dielectric material layer. An upperinterconnect level is located above the lower interconnect level and itincludes second metal-containing structures embedded within a secondinterconnect dielectric material layer. A resistor is present in theupper interconnect level. In accordance with this embodiment, theresistor has a bottommost surface that is coplanar with a topmostsurface of the first interconnect dielectric material layer and atopmost surface that is located entirely beneath a topmost surface ofthe second interconnect dielectric material layer. A dielectric capcovers an entirety of the topmost surface of the resistor.

In another embodiment, the semiconductor structure includes a lowerinterconnect level including a pair of spaced apart metal-containingportions embedded within an interconnect dielectric material layer. Anupper interconnect level is located above the lower interconnect leveland includes metal-containing structures embedded within a dielectricmaterial layer, wherein each metal-containing structure is locateddirectly above one of the metal-containing portions of the pair ofmetal-containing portions. A resistor is present in the lowerinterconnect level and between the pair of spaced apart metal-containingportions. A dielectric material (i.e., a dielectric cap or a dielectricmaterial layer) is present on the entirety of the resistor.

In one embodiment, the method includes providing an interconnect levelcomprising metal-containing structures embedded within an interconnectdielectric material layer, wherein a diffusion barrier liner is presenton sidewalls and a bottom wall of each metal-containing structure. Next,a patterned hard mask is formed on the interconnect level, wherein thepatterned hard mask has an opening that physically exposes one of themetal-containing structures and the diffusion barrier liner thatsurrounds the physically exposed metal-containing structure. Verticalsidewall portions of the physically exposed diffusion barrier liner areremoved, while maintaining a portion of the diffusion barrier linerbeneath the physically exposed metal-containing structure, wherein theportion of the diffusion barrier liner that remains beneath thephysically exposed metal-containing structure defines a resistor. Next,the physically exposed metal-containing structure is removed tophysically expose the resistor, followed by the removal of the patternedhard mask. A dielectric stack is then formed above the resistor and theinterconnect level.

In another embodiment, the method includes providing an interconnectlevel comprising a metal-containing structure embedded within aninterconnect dielectric material layer, wherein a diffusion barrierliner is present on the sidewalls and a bottom wall of themetal-containing structure. Next, a patterned hard mask is formed on theinterconnect level, wherein the patterned hard mask has an opening thatphysically exposes a portion of the metal-containing structure. Thephysically exposed portion of the metal-containing structure is removedto physically expose a portion of the diffusion barrier liner, whereinthe physically exposed portion of the diffusion barrier liner defines aresistor that is present along a bottom portion of a resistor cavitythat is formed between remaining portions of the metal-containingstructure. The patterned hard mask is then removed and, thereafter, adielectric material layer is formed above the interconnect level andabove the resistor. Next, metal-containing structures are formed withinthe dielectric material layer and above each remaining portion of themetal-containing structure.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross sectional view of an exemplary semiconductor structureduring an early stage of fabrication and including a patterned hard maskthat is formed on an upper interconnect level in accordance with a firstembodiment of the present application.

FIG. 2 is a cross sectional view of the exemplary semiconductorstructure of FIG. 1 after removing vertical sidewall portions of adiffusion barrier liner that is present in the upper interconnect leveland that is not protected by the patterned hard mask.

FIG. 3 is a cross sectional view of the exemplary semiconductorstructure of FIG. 2 after removing the interconnect metal-containingstructure that is present in the upper interconnect level and that isnot protected by the patterned hard mask.

FIG. 4 is a cross sectional view of the exemplary semiconductorstructure of FIG. 3 after removing the patterned hard mask, and forminga dielectric stack of a dielectric cap and a dielectric material layer.

FIG. 5 is a cross sectional view of the exemplary semiconductorstructure of FIG. 2 after removing end portions of a remaininghorizontal portion of the diffusion barrier liner in accordance with avariation of the first embodiment of the application.

FIG. 6 is a cross sectional view of the exemplary semiconductorstructure of FIG. 5 after removing the interconnect metal-containingstructure that is present in the upper interconnect level and that isnot protected by the patterned hard mask, removing the patterned hardmask, and forming a dielectric stack of a dielectric cap and adielectric material layer.

FIG. 7 is a cross sectional view of an exemplary semiconductor structureduring an early stage of fabrication including a capping layer that islocated on a lower interconnect level in accordance with a secondembodiment of the present application.

FIG. 8 is a cross sectional view of the exemplary structure of FIG. 7after forming a patterned hard mask on the capping layer, the patternedhard mask including an opening that physically exposes a portion of thecapping layer.

FIG. 9 is a cross sectional view of the exemplary semiconductorstructure of FIG. 8 after removing the physically exposed portion of thecapping layer and a metal-containing structure that is located beneaththe physically exposed portion of the capping layer.

FIG. 10 is a cross sectional view of the exemplary semiconductorstructure of FIG. 9 after removing the patterned hard mask, and forminga dielectric stack of a dielectric cap and a dielectric material layer.

FIG. 11 is a cross sectional view of the exemplary structure of FIG. 10after forming an upper interconnect level within the dielectric materiallayer of the dielectric stack.

DETAILED DESCRIPTION

The present application will now be described in greater detail byreferring to the following discussion and drawings that accompany thepresent application. It is noted that the drawings of the presentapplication are provided for illustrative purposes only and, as such,the drawings are not drawn to scale. It is also noted that like andcorresponding elements are referred to by like reference numerals.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide an understanding ofthe various embodiments of the present application. However, it will beappreciated by one of ordinary skill in the art that the variousembodiments of the present application may be practiced without thesespecific details. In other instances, well-known structures orprocessing steps have not been described in detail in order to avoidobscuring the present application.

It will be understood that when an element as a layer, region orsubstrate is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “beneath” or “under” another element, it can bedirectly beneath or under the other element, or intervening elements maybe present. In contrast, when an element is referred to as being“directly beneath” or “directly under” another element, there are nointervening elements present.

Referring first to FIG. 1, there is illustrated an exemplarysemiconductor structure during an early stage of fabrication and inaccordance with a first embodiment of the present application. Theexemplary semiconductor structure shown in FIG. 1 includes a patternedhard mask 26 that is formed on an upper interconnect level, L_(n+1), ofan interconnect structure 10. The patterned hard mask 26 includes anopening 28 that physically exposes an area of the upper interconnectlevel, L_(n+1), in which a precision BEOL resistor in accordance withthe present application will be subsequently formed. The patterned hardmask 26 covers interconnect device areas of the exemplary structure,i.e., areas in which interconnect metal-containing structures are toremain. The upper interconnect level, L_(n+1), is located above a lowerinterconnect level L_(n). In the present application, n is an integerstarting at 1. In the illustrated embodiment, capping layer 18 ispositioned between the lower interconnect level, L_(n), and the upperinterconnect level, L_(n+1). In some embodiments, capping layer 18 isomitted.

The lower interconnect level, L_(n), includes a first interconnectdielectric material layer 12 that includes a plurality of firstmetal-containing structures 16 embedded therein; the firstmetal-containing structures are electrically conductive. A firstdiffusion barrier liner 14 is also present that surrounds the sidewallsand the bottom wall (i.e., bottommost surface) of each firstmetal-containing structures 16 which is embedded in the firstinterconnect dielectric material layer 12. As is shown, the firstmetal-containing structures 16 and the first diffusion barrier liners 14have topmost surfaces that are coplanar with each other as well ascoplanar with a topmost surface of the first interconnect dielectricmaterial layer 12. In some embodiments, the first diffusion barrierliners 14 may be omitted from the lower interconnect level, L_(n). Insome embodiments, the first interconnect dielectric material layer 12may extend beneath each first metal-containing structure 16 so as tocompletely embed the first metal-containing structures 16.

The first interconnect dielectric material layer 12 of the lowerinterconnect level, L_(n), may be composed of an inorganic dielectricmaterial or an organic dielectric material. In some embodiments, firstinterconnect dielectric material layer 12 may be porous. In otherembodiments, the first interconnect dielectric material layer 12 may benon-porous. Examples of suitable dielectric materials that may beemployed as the first interconnect dielectric material layer 12 include,but are limited to, silicon dioxide, undoped or doped silicate glass,silsesquioxanes, C doped oxides (i.e., organosilicates) that includeatoms of Si, C, O and H, theremosetting polyarylene ethers or anymultilayered combination thereof. The term “polyarylene” is used in thispresent application to denote aryl moieties or inertly substituted arylmoieties which are linked together by bonds, fused rings, or inertlinking groups such as, for example, oxygen, sulfur, sulfone, sulfoxide,or carbonyl.

The first interconnect dielectric material layer 12 may have adielectric constant (all dielectric constants mentioned herein aremeasured relative to a vacuum, unless otherwise stated) that is about4.0 or less. In one embodiment, the first interconnect dielectricmaterial layer 12 has a dielectric constant of 2.8 or less. Thesedielectrics generally having a lower parasitic cross talk as compared todielectric materials whose dielectric constant is greater than 4.0.

The first interconnect dielectric material layer 12 may be formed by adeposition process such as, for example, chemical vapor deposition(CVD), plasma enhanced chemical vapor deposition (PECVD) or spin-oncoating. The first interconnect dielectric material layer 12 may have athickness from 50 nm to 250 nm. Other thicknesses that are lesser than50 nm, and greater than 250 nm can also be employed in the presentapplication.

After providing the first interconnect dielectric material layer 12,openings (not shown) are formed into the first interconnect dielectricmaterial layer 12; each opening will house a first metal-containingstructure 16 and, if present, the first diffusion barrier liner 14. Theopenings in the first interconnect dielectric material layer 12 may bevia openings, line openings and/or combined via/lines openings. Theopenings may be formed by lithography and etching. In embodiments inwhich a combined via/line opening is formed, a second iteration oflithography and etching may be used to form such an opening.

In some embodiments, a first diffusion barrier material is then formedwithin each opening and on an exposed topmost surface of the firstinterconnect dielectric material layer 12; the first diffusion barriermaterial will provide the first diffusion barrier liner 14 mentionedabove. The first diffusion barrier material may include Ta, TaN, Ti,TiN, Ru, RuN, RuTa, RuTaN, W, WN or any other material that can serve asa barrier to prevent a conductive material from diffusing there through.The thickness of the first diffusion barrier material may vary dependingon the deposition process used as well as the material employed. In someembodiments, the first diffusion barrier material may have a thicknessfrom 2 nm to 50 nm; although other thicknesses for the diffusion barriermaterial are contemplated and can be employed in the present applicationas long as the first diffusion barrier material does not entirely fillthe opening. The first diffusion barrier material can be formed by adeposition process including, for example, chemical vapor deposition(CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layerdeposition (ALD), physical vapor deposition (PVD), sputtering, chemicalsolution deposition or plating.

In some embodiments, an optional plating seed layer (not specificallyshown) can be formed on the surface of the first diffusion barriermaterial. In cases in which the conductive material to be subsequentlyand directly formed on the first diffusion barrier material, theoptional plating seed layer is not needed. The optional plating seedlayer is employed to selectively promote subsequent electroplating of apre-selected conductive metal or metal alloy. The optional plating seedlayer may be composed of Cu, a Cu alloy, Ir, an Ir alloy, Ru, a Ru alloy(e.g., TaRu alloy) or any other suitable noble metal or noble metalalloy having a low metal-plating overpotential. Typically, Cu or a Cualloy plating seed layer is employed, when a Cu metal is to besubsequently formed within the at least one opening. The thickness ofthe optional plating seed layer may vary depending on the material ofthe optional plating seed layer as well as the technique used in formingthe same. Typically, the optional plating seed layer has a thicknessfrom 2 nm to 80 nm. The optional plating seed layer can be formed by aconventional deposition process including, for example, CVD, PECVD, ALD,or PVD.

Next, a first interconnect metal or metal alloy is then formed into eachopening and, if present, atop the first diffusion barrier material. Thefirst interconnect metal or metal alloy provides the firstmetal-containing structures 16 of the present application. The firstinterconnect metal or metal alloy can be formed utilizing a depositionprocess such as, for example, CVD, PECVD, sputtering, chemical solutiondeposition or plating. In one embodiment, a bottom-up plating process isemployed in forming the first interconnect metal or metal alloy. In someembodiments, the first interconnect metal or metal alloy is formed abovethe topmost surface of the first interconnect dielectric material layer12.

Following the deposition of the first interconnect metal or metal alloy,a planarization process such as, for example, chemical mechanicalpolishing (CMP) and/or grinding, can be used to remove all interconnectmetal or metal alloy (i.e., overburden material) that is present outsideeach of the openings forming the first metal-containing structures 16shown in FIG. 1. The planarization stops on a topmost surface of thefirst interconnect dielectric material layer 12. Thus, and if present,the planarization process also removes the first diffusion barriermaterial from the topmost surface of the first interconnect dielectricmaterial layer 12. The remaining portion of the first diffusion barriermaterial that is present in each opening is referred to herein as thefirst diffusion barrier liner 14, while the remaining first interconnectmetal or metal alloy that is present in each opening may be referred toas the first metal-containing structure 16. Collectively, the firstinterconnect dielectric material layer 12, each optional first diffusionbarrier liner 14, and each first metal-containing structure 16 definethe lower interconnect level, L_(n), of the present application.

Next, and in some embodiments, a capping layer 18 can be formed on thephysically exposed topmost surface of the lower interconnect level,L_(n), of the present application. In some embodiments, capping layer 18can be omitted. When present, the capping layer 18 may include anydielectric material such as, for example, silicon carbide (SiC), siliconnitride (Si₃N₄), silicon dioxide (SiO₂), a carbon doped oxide, anitrogen and hydrogen doped silicon carbide (SiC(N,H)) or a multilayeredstack of at least one of the aforementioned dielectric cappingmaterials. The capping material that provides the capping layer 18 maybe formed utilizing a deposition process such as, for example, CVD,PECVD, ALD, chemical solution deposition or evaporation. When present,capping layer 18 may have a thickness from 10 nm to 100 nm. Otherthicknesses that are lesser than 10 nm, or greater than 100 nm may alsobe used as the thickness of the capping layer 18.

In the illustrated embodiment of FIG. 1, the upper interconnect level,L_(n+1), is then formed on the capping layer 18. When the capping layer18 is omitted, the upper interconnect level, L_(n+1), can be formed uponthe lower interconnect level, L_(n).

The upper interconnect level, L_(n+1), includes a second interconnectdielectric material layer 20, second diffusion barrier liners 22, andsecond metal-containing structures 24; the second metal-containingstructures are electrically conductive. As is shown in FIG. 1, eachsecond diffusion barrier liner 22 is present on the sidewalls and bottomwall (and thus surrounds) each second metal-containing structure 24. Asis shown, the second metal-containing structures 24 and the seconddiffusion barrier liners 22 have topmost surfaces that are coplanar witheach other as well as coplanar with a topmost surface of the secondinterconnect dielectric material layer 20. In the illustratedembodiment, a bottommost surface of a horizontal portion of each seconddiffusion barrier liner 22 contacts a topmost surface of at least one ofthe underlying first metal-containing structures 16. It is noted thatsome of the second metal-containing structures 24 will be maintained inthe second interconnect dielectric material layer 20, while at least oneof the second metal-containing structures 16 that is present in a via orline opening and within a resistor area of the exemplary structure willbe further processed herein to provide a precision resistor of thepresent application.

The second interconnect dielectric material layer 20 may include one ofthe interconnect dielectric materials mentioned above for the firstinterconnect dielectric material layer 12. In some embodiments, thesecond interconnect dielectric material layer 20 includes a sameinterconnect dielectric material as the first interconnect dielectricmaterial layer 12. In other embodiments, the second interconnectdielectric material layer 20 includes a different interconnectdielectric material than the first interconnect dielectric materiallayer 12. The second interconnect dielectric material layer 20 may beporous or non-porous, have a thickness within the thickness range of thefirst interconnect dielectric material layer 12, and be formed utilizingone of the deposition processes used in providing the first interconnectdielectric material layer 12.

Openings can then be formed into the second interconnect dielectricmaterial layer 20 and, if present, capping layer 18. The openings thatare formed into the second interconnect dielectric material layer 20and, if present, capping layer 18 may include line openings, viaopenings, and/or combined via/line openings, with the proviso that atleast one of the openings in a resistor area of the exemplary structurewill be a via opening or a line opening. The openings are formed bylithography and etching as defined above.

A second diffusion barrier material and a second interconnect metal ormetal alloy can then be formed into the openings that are formed intothe second interconnect dielectric material layer 20 and, if present,capping layer 18 and atop the second interconnect dielectric materiallayer 20. The second diffusion barrier material may include one of thediffusion barrier materials mentioned above for the first diffusionbarrier material. In one embodiment, the first and second diffusionbarrier materials may be composed of a same diffusion barrier material.In another embodiment, the first and second diffusion barrier materialsare composed of different diffusion barrier materials. The seconddiffusion barrier material may be formed utilizing one of the depositionprocesses mentioned above for forming the first diffusion barriermaterial, and the second diffusion barrier material may have a thicknesswithin the thickness range mentioned above for the first diffusionbarrier material. After forming the second diffusion barrier material,an optional plating seed layer may be formed.

Next, the second interconnect metal or metal alloy is formed above thesecond diffusion barrier material. The second interconnect metal ormetal alloy may include one of the interconnect metals or metal alloysmentioned above for the first interconnect metal or metal alloy. In oneembodiment, the first interconnect metal or metal alloy is a sameinterconnect metal or metal alloy as the second interconnect metal ormetal alloy. In another embodiment, the first interconnect metal ormetal alloy is a different interconnect metal or metal alloy than thesecond interconnect metal or metal alloy. The second interconnect metalor metal alloy may be formed utilizing one of the techniques mentionedabove for forming the first interconnect metal or metal alloy.

Following the deposition of the second interconnect metal or metalalloy, a planarization process such as, for example, chemical mechanicalpolishing (CMP) and/or grinding, can be used to remove all interconnectmetal or metal alloy (i.e., overburden material) that is present outsideeach the opening forming the second metal-containing structures 24 shownin FIG. 1. The planarization stops on a topmost surface of the secondinterconnect dielectric material layer 20. The planarization processalso removes the second diffusion barrier material from the topmostsurface of the second interconnect dielectric material layer 20. Theremaining portion of the second diffusion barrier material that ispresent in each opening is referred to herein as the second diffusionbarrier liner 22, while the remaining second interconnect metal or metalalloy that is present in each opening may be referred to as the secondmetal-containing structure 24. Collectively, the second interconnectdielectric material layer 20, each second diffusion barrier liner 22,and each second metal-containing structure 24 define the upperinterconnect level, L_(n+1), of the present application.

Next, a layer of hard mask material is formed on a physically exposedsurface of the upper interconnect level, L_(n+1), and then the layer ofhard mask material is patterned by lithography and etching to providepatterned hard mask 26 having opening 28. The opening 28 that is formedinto the layer of hard mask material defines an area in the structure inwhich a precision BEOL resistor will be subsequently formed. Although asingle opening 28 is shown and described, a plurality of openings may beformed into the layer of hard mask material to define areas in whichother BEOL resistors can be formed. The patterned hard mask 26 mayinclude a dielectric hard mask material such as, for example, siliconnitride or silicon oxynitride. The layer of hard mask material may beformed utilizing a deposition process such as, for example, CVD, PECVD,or physical vapor deposition (PVD). The layer of hard mask material mayhave a thickness from 10 nm to 50 nm; other thicknesses can also be usedas the thickness of the hard mask material.

The opening 28 that is present in the patterned hard mask 26 physicallyexposes a second metal-containing structure 24 and a second diffusionbarrier liner 22 that is within the resistor area of the exemplarystructure. Portions of the second interconnect dielectric material layer20 in the resistor area may also be physically exposed by opening 28.

Referring now to FIG. 2, there is illustrated the exemplarysemiconductor structure of FIG. 1 after removing vertical sidewallportions of the second diffusion barrier liner 22 that is present in theresistor area and that is not protected by the patterned hard mask 26.The vertical sidewall portions of the physically exposed seconddiffusion barrier liner 22 may be removed utilizing an etch process thatis selective in removing the second diffusion barrier material relativeto the interconnect dielectric material that provides the secondinterconnect dielectric material layer 20 or the interconnect metal ormetal alloy that provides the second metal-containing structure 24. Inone embodiment, the etch may be a dry etching process such as, forexample, reactive ion etching or plasma etching. In another embodiment,the etch may be a chemical wet etch process in which a chemical etchantis employed. In one example, and when TaN is employed as the diffusionbarrier material of the second diffusion barrier liner 22, a mixture ofacids and chemical compounds, such as, for example, hydrogen, fluoride,hydrogen chloride, nitric acid and sulfuric acid, can be used to removethe vertical portions of the physically exposed second diffusion barrierliner 22.

After etching of the vertical sidewall portions of the physicallyexposed second diffusion barrier liner 22, a horizontal portion of thephysically exposed second diffusion barrier liner 22 remains. Thisremaining horizontal portion of the physically exposed second diffusionbarrier liner 22 may be referred to herein as resistor 22R. In thisembodiment, the resistor 22R has a bottommost surface that contacts atleast one of the underlying first metal-containing structures 16 of thelower interconnect level, L_(n).

Referring now to FIG. 3, there is illustrated the exemplarysemiconductor structure of FIG. 2 after removing the physically exposedsecond interconnect metal-containing structure 24 that is not protectedby the patterned hard mask 26; as is shown the entirety of thephysically exposed second interconnect metal-containing structure 24 isremoved so as to physically expose the underlying resistor 22R.

The physically exposed second interconnect metal-containing structure 24can be removed utilizing an etch process that is selective in removingthe second interconnect metal or metal alloy that provides the secondmetal-containing structure 24 relative to the material of resistor 22Rand the interconnect dielectric material that provides the secondinterconnect dielectric material layer 20. In one embodiment, the etchmay be a dry etching process such as, for example, reactive ion etchingor plasma etching. In another embodiment, the etch may be a chemical wetetch process in which a chemical etchant is employed. In one example,and when Cu is employed as the second interconnect metal or metal alloy,a mixture of acids and chemical compounds, such as, for example,hydrogen, fluoride, hydrogen chloride, nitric acid and sulfuric acid,can be used to remove the vertical sidewall portions of the physicallyexposed second metal-containing structure 24.

Referring now to FIG. 4, there is illustrated the exemplarysemiconductor structure of FIG. 3 after removing the patterned hard mask26, and forming a dielectric stack of a dielectric cap 30 and adielectric material layer 32. In this embodiment, the topmost surface ofthe resistor 22R is entirely covered by the dielectric cap 30. Thepatterned hard mask 26 may be removed by utilizing any conventionalmaterial removal process such as, for example, chemical mechanicalpolishing.

The dielectric cap 30 includes one of the dielectric materials mentionedabove for capping layer 18. In one embodiment, dielectric cap 30includes a same dielectric material as capping layer 18. In anotherembodiment, dielectric cap 30 may include a different dielectricmaterial than capping layer 18. Dielectric cap 30 may be formedutilizing one of the deposition processes mentioned above for formingcapping layer 18, and dielectric cap 30 may have a thickness within thethickness range mentioned above for capping layer 18.

The dielectric material layer 32 may include one of the interconnectdielectric materials mentioned above for the first interconnectdielectric material 12. The dielectric material layer 32 may be formedutilizing one of the deposition processes mentioned above for formingthe first interconnect dielectric material layer 12. In someembodiments, a planarization process may follow the deposition of thedielectric material that provides the dielectric material layer 32.Dielectric material layer 32 is composed of a different dielectricmaterial than dielectric cap 30.

FIG. 4 illustrates one exemplary structure of the present application.Notably, the exemplary structure of FIG. 4 includes a lower interconnectlevel, L_(n), including first metal-containing structures 16 embeddedwithin a first interconnect dielectric material layer 12. An upperinterconnect level, L_(n+1), is located above the lower interconnectlevel, L_(n), and the upper interconnect level, L_(n+1), includes secondmetal-containing structures 24 embedded within a second interconnectdielectric material layer 20. A resistor 22R is present in the upperinterconnect level, L_(n+1). In accordance with this embodiment, theresistor 22R has a bottommost surface that is coplanar with a topmostsurface of the first interconnect dielectric material layer 12 and atopmost surface that is located entirely beneath a topmost surface ofthe second interconnect dielectric material layer 20. In thisembodiment, a dielectric cap 30 is present on an entirety of the topmostsurface of the resistor 22R. It is noted that the resistor 22R and thesecond metal-containing structures 24 (interconnect structures) arepresent in a same interconnect level as each other. Also, the resistor22R and the second diffusion barrier liners 22 that remain in theinterconnect area are composed of a same diffusion barrier material.Further, the exemplary structure of FIG. 4 is devoid of any metallicstructure that contacts a topmost surface of the resistor 22R.

In this embodiment, at least a portion of a bottommost surface of theresistor 22R directly contacts a topmost surface portion of aneighboring pair of first metal-containing structures 16 embedded withinthe first interconnect dielectric material layer 12; no upper contact isneeded. Notably, end portions of the bottommost surface of the resistor22R directly contact a topmost surface of a neighboring pair of firstmetal-containing structures 16 embedded within the first interconnectdielectric material layer 12.

Referring now to FIG. 5, there is illustrated the exemplarysemiconductor structure of FIG. 2 after removing end portions of aremaining horizontal portion of the diffusion liner (i.e., the resistor22R) in accordance with a variation of the first embodiment of theapplication. In this embodiment, the remaining resistor 22R is trimmedto a desired length and does not directly contact any of the underlyingfirst metal-containing structures 16 that are present in the lowerinterconnect level, L1. This step of the present application may beperformed utilizing a laterally etching process that is selective inremoving the end portions of the resistor 22R.

Referring now to FIG. 6, there is illustrated the exemplarysemiconductor structure of FIG. 5 after removing the secondmetal-containing structure 24 that is not protected by the patternedhard mask 26, removing the patterned hard mask 26, and forming adielectric stack of a dielectric cap 30 and a dielectric material layer32. The removal of the second metal-containing structure 24 and thepatterned hard mask 26 of this variation of the present application areperformed utilizing the techniques mentioned above in the previouslyembodiment of the present application; See, for example, the descriptionprovided above for FIG. 3 (second metal-containing structure removal)and FIG. 4 (patterned hard mask removal). The dielectric stack includingthe dielectric cap 30 and the dielectric material layer 32 can be formedand include materials as described above in FIG. 4 of the presentapplication.

FIG. 6 illustrates another exemplary structure of the presentapplication. Notably, the exemplary structure of FIG. 6 includes a lowerinterconnect level, L_(n), including first metal-containing structures16 embedded within a first interconnect dielectric material layer 12. Anupper interconnect level, L_(n+1), is located above the lowerinterconnect level, L_(n), and the upper interconnect level, L_(n+1)includes second metal-containing structures 24 embedded within a secondinterconnect dielectric material layer 20. A resistor 22R is present inthe upper interconnect level, L_(n+1). In accordance with thisembodiment, the resistor 22R has a bottommost surface that is coplanarwith a topmost surface of the first interconnect dielectric materiallayer 12 and a topmost surface that is located entirely beneath atopmost surface of the second interconnect dielectric material layer 20.In this embodiment, a dielectric cap 30 is present on an entirety of thetopmost surface of the resistor 22R and a portion of the dielectric cap30 contacts sidewalls of the resistor 22R. It is noted that the resistor22R and the second metal-containing structures 24 (interconnectstructures) are present in a same interconnect level as each other.Also, the resistor 22R and the second diffusion barrier liners 22 thatremain in the interconnect area are composed of a same diffusion barriermaterial. Further, the exemplary structure of this embodiment is devoidof any metallic structure that contacts a topmost surface of theresistor.

In this embodiment, an entirety of the bottommost surface of theresistor 22R directly contacts a topmost surface of the firstinterconnect dielectric material layer 12. Such a structure has improvedcooling as compared to the structure shown in FIG. 4. In thisembodiment, dielectric cap 30 directly contacts the sidewall surfaces ofthe resistor 22R which has been trimmed.

Referring now to FIG. 7, there is illustrated an exemplary semiconductorstructure during an early stage of fabrication in accordance with asecond embodiment of the present application. The exemplary structure ofFIG. 7 includes a capping layer 56 that is located on an interconnectlevel, L_(n). The interconnect level, L_(n), of this embodiment of thepresent application includes an interconnect dielectric material layer50 having a metal-containing structure 54 embedded therein. As is shown,a diffusion barrier liner 52 is present on the sidewalls and along abottom wall of the metal-containing structure 54 thus separating themetal-containing structure 54 from the interconnect dielectric materiallayer 50. The diffusion barrier liner 52 and the metal-containingstructure 54 have topmost surfaces that are coplanar with each other aswell as being coplanar with a topmost surface of the interconnectdielectric material layer 50.

The interconnect dielectric material layer 50 of this embodiment of thepresent application may include one of the interconnect dielectricmaterials mentioned above for the first interconnect dielectric materiallayer 12. The interconnect dielectric material layer 50 may be porous ornon-porous, have a thickness within the thickness range of the firstinterconnect dielectric material layer 12, and be formed utilizing oneof the deposition processed used in providing the first interconnectdielectric material layer 12.

Openings can then be formed into the interconnect dielectric materiallayer 50; in the drawings of this embodiment a single opening is formedand further processed as described herein below. In this embodiment, theopening in the resistor area is a line opening. The openings are formedby lithography and etching as defined above.

A diffusion barrier material and an interconnect metal or metal alloycan then be formed into the openings that are formed into theinterconnect dielectric material layer 50 and atop the interconnectdielectric material layer 50. The diffusion barrier material may includeone of the diffusion barrier materials mentioned above for the firstdiffusion barrier material. The diffusion barrier material of thisembodiment may be formed utilizing one of the deposition processesmentioned above for forming the first diffusion barrier material, andthe diffusion barrier material of this embodiment may have a thicknesswithin the thickness range mentioned above for the first diffusionbarrier material. After forming the diffusion barrier material, anoptional plating seed layer may be formed.

Next, the interconnect metal or metal alloy is formed above thediffusion barrier material. The interconnect metal or metal alloy mayinclude one of the metals or metal alloys mentioned above for the firstinterconnect metal or metal alloy. The interconnect metal or metal alloymay be formed utilizing one of the techniques mentioned above forforming the first interconnect metal or metal alloy.

Following the deposition of the interconnect metal or metal alloy, aplanarization process such as, for example, chemical mechanicalpolishing (CMP) and/or grinding, can be used to remove all interconnectmetal or metal alloy (i.e., overburden material) that is present outsideeach the opening forming the metal-containing structure 54 shown in FIG.7. The planarization stops on a topmost surface of the interconnectdielectric material layer 50. Thus, the planarization process alsoremoves the diffusion barrier material from the topmost surface of theinterconnect dielectric material layer 50. The remaining portion of thediffusion barrier material that is present the opening is referred toherein as the diffusion barrier liner 52, while the remaininginterconnect metal or metal alloy that is present in the opening may bereferred to as the metal-containing structure 54. Collectively, theinterconnect dielectric material layer 50, the diffusion barrier liner52, and the metal-containing structure 54 define the interconnect level,L_(n), of this embodiment of the present application.

Next, the capping layer 56 is formed upon the interconnect level, L_(n).The capping layer 56 may include one of the dielectric capping materialsmentioned above for capping layer 18. The capping layer 56 of thisembodiment may be formed utilizing one of the deposition processesmentioned above for forming the capping layer 18, and the capping layer56 of this embodiment may have a thickness within the thickness rangementioned above for the capping layer 18.

Referring now to FIG. 8, there is illustrated the exemplary structure ofFIG. 7 after forming a patterned hard mask 58 on the capping layer 56,the patterned hard mask 58 includes an opening 60 the physically exposesa portion of the capping layer 56. The opening 60 that is formed definesan area in the structure in which a precision BEOL resistor will besubsequently formed. The patterned hard mask 58 may include one of thehard mask materials mentioned above for patterned hard mask 26. The hardmask material that provides the patterned hard mask 58 of thisembodiment may be formed utilizing one of the deposition processesmentioned above for forming the hard mask material for providingpatterned hard mask 26, and the hard mask material that provides thepatterned hard mask 58 of this embodiment may have a thickness withinthe thickness range mentioned above for the hard mask material forproviding patterned hard mask 26. Patterning of the hard mask materialmay be performed by lithography and etching.

Referring now to FIG. 9, there is illustrated the exemplarysemiconductor structure of FIG. 8 after removing the physically exposedportion of the capping layer 56 and the metal-containing structure 54that is located beneath the physically exposed portion of the cappinglayer 56. The removal of the physically exposed portion of the cappinglayer 56 and the metal-containing structure 54 may be performedutilizing one or more etching processes. In one example, a first etch isused to open the capping layer 56, while a second etch is used to removethe metal-containing structure 54. In yet another example, a single etchis used to remove the physically exposed portion of the capping layer 56and the metal-containing structure 54. Notwithstanding whether a singleetch or a two step etch process is used, the at least one etchingincludes an anisotropic etch such as, for example, reaction ion etching.After removing the metal-containing structure 54 that is located beneaththe physically exposed portion of the capping layer 56, a portion of thediffusion barrier liner 52 within a resistor cavity 61 is now physicallyexposed. The physically exposed portion of the diffusion barrier liner52 may be referred to herein as a resistor 52R.

As is shown in FIG. 9, portions of the metal-containing structure 54remaining laterally adjacent the resistor cavity 61. The remainingportions of the metal-containing structure 54 are referred to herein asmetal-containing portions 54P; each metal-containing portion 54P iselectrically conductive.

Referring now to FIG. 10, there is illustrated the exemplarysemiconductor structure of FIG. 9 after removing the patterned hard mask58, and forming a dielectric stack of a dielectric cap 62 and adielectric material layer 64. In some embodiments, dielectric cap 62 maybe omitted. The patterned hard mask 58 may be removed utilizing anymaterial removal process such as, for example, planarization. Thedielectric stack including the optional dielectric cap 62 and thedielectric material layer 64 can be formed and include materials asdescribed above in FIG. 4 of the present application.

Referring now to FIG. 11, there is illustrated the exemplary structureof FIG. 10 after forming an upper interconnect level, L_(n+1), withinthe dielectric material layer 64 of the dielectric stack. The forming ofthe upper interconnect level, L_(n+1), includes forming openings intothe dielectric material layer 64, and optionally into the cap layer 62by lithography and etching and then forming a diffusion barrier liner 66and a metal-containing structure 68 into the openings. The diffusionbarrier liner 66 and the metal-containing structure 68 include materialsas described above for the first diffusion barrier liners 14 and firstmetal-containing structures 16. The diffusion barrier liner 66 and themetal-containing structure 68 can be formed utilizing techniques asmentioned above for forming the first diffusion barrier liner and firstmetal-containing structure. As is shown, the diffusion barrier liner 66and the metal-containing structure 68 that provide the upperinterconnect level, L_(n+1), are located directly above the remainingmetal-containing structures 54P that are present in the lowerinterconnect level, L_(n).

FIG. 11 exemplifies another semiconductor structure in accordance withthe present application. The exemplary structure of FIG. 11 includes alower interconnect level, L_(n), including a pair of spaced apartmetal-containing portions 54P embedded within an interconnect dielectricmaterial layer 50. An upper interconnect level, L_(n+1), is locatedabove the lower interconnect level, L_(n), and includes metal-containingstructures 68 embedded within a dielectric material layer 64, whereineach metal-containing structure 68 is located directly above one of themetal-containing portions 54P of the pair of spaced apartmetal-containing portions. A resistor 52R in the lower interconnectlevel and between the pair of spaced apart metal-containing portions54P. In this embodiment, the metal-containing portions 54P within theinterconnect dielectric material layer 50 provide contact (i.e., fromthe sides) to the resistor 52R; no metallic structure is present thatcontacts a topmost surface of the resistor.

It is noted that the resistors shown in FIGS. 4, 6, and 11 are precisionBEOL resistors, without any metallic structures that contact a topmostsurface of the resistor, that have small tolerances of variation and arereadily integrated in with the overall BEOL process flow in a way thatminimizes cost, space and/or wiring congestion.

While the present application has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present application. It is therefore intended that the presentapplication not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. A semiconductor structure comprising: a lowerinterconnect level including first metal-containing structures embeddedwithin a first interconnect dielectric material layer; an upperinterconnect level located above the lower interconnect level andcomprising second metal-containing structures embedded within a secondinterconnect dielectric material layer; a resistor present in the upperinterconnect level, wherein the resistor has a bottommost surface thatis coplanar with a topmost surface of the first interconnect dielectricmaterial layer and a topmost surface that is located entirely beneath atopmost surface of the second interconnect dielectric material layer;and a continuous dielectric cap located directly on an entirety of thetopmost surface of the resistor, directly on a topmost surface of thesecond interconnect dielectric material layer, and directly on a topmostsurface of the second metal-containing structures.
 2. The semiconductorstructure of claim 1, wherein at least a portion of the bottommostsurface of the resistor directly contacts a topmost surface of at leastone of the first metal-containing structures embedded within the firstinterconnect dielectric material layer.
 3. The semiconductor structureof claim 1, wherein end portions of the bottommost surface of theresistor directly contact a topmost surface of a neighboring pair offirst metal-containing structures embedded within the first interconnectdielectric material layer.
 4. The semiconductor structure of claim 1,wherein an entirety of the bottommost surface of the resistor directlycontains a topmost surface of the first interconnect dielectric materiallayer.
 5. The semiconductor structure of claim 1, further comprising acapping layer located between the lower interconnect level and the upperinterconnect level.
 6. The semiconductor structure of claim 1, wherein adiffusion barrier liner is present on sidewalls and along a bottom wallof each second metal-containing structure, and wherein the diffusionbarrier liner and the resistor comprise a same diffusion barriermaterial.
 7. The semiconductor structure of claim 6, wherein thediffusion barrier material comprises Ta, TaN, Ti, TiN, Ru, RuN, RuTa,RuTaN, W, or WN.
 8. The semiconductor structure of claim 1, furthercomprising a dielectric material layer located on the dielectric cap. 9.The semiconductor structure of claim 1, wherein the structure is devoidof any metallic structure that contacts the topmost surface of theresistor.
 10. The semiconductor structure of claim 1, wherein thedielectric cap further directly contacts sidewall surfaces of theresistor.